Connecting material, method for manufacturing connecting material and semiconductor device

ABSTRACT

In a connecting material of the present invention, a Zn series alloy layer is formed on an outermost surface of an Al series alloy layer. In particular, in the connecting material, an Al content of the Al series alloy layer is 99 to 100 wt.% or a Zn content of the Zn series alloy layer is 90 to 100 wt.%. By using this connecting material, the formation of an Al oxide film on the surface of the connecting material at the time of the connection can be suppressed, and preferable wetness that cannot be obtained with the Zn—Al alloy can be obtained. Further, a high connection reliability can be achieved when an Al series alloy layer is left after the connection, since the soft Al thereof functions as a stress buffer material.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent ApplicationNo. JP 2006-314168 filed on Nov. 21, 2006, the content of which ishereby incorporated by reference into this application.

This application is a Continuing application of Application No.13/228,169, filed Sep. 8, 2011, which is a Divisional application ofApplication No. 11/943,632, filed Nov. 21, 2007, the contents of whichare incorporated herein by reference in their entirety.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a technology for a connecting material.More particularly, the present invention relates to a technologyeffectively applied to a structure and a manufacturing method of theconnecting material, and a semiconductor device, a power semiconductordevice and a power module using the connecting material.

BACKGROUND OF THE INVENTION

As a technology that the inventors of the present invention have beenexamined, a semiconductor device using a connecting material will bedescribed with reference to FIG. 1 and FIG. 2.

FIG. 1 is a diagram showing a structure of a conventional semiconductordevice. FIG. 2 is a diagram for explaining the flash caused by remeltedsolder.

As shown in FIG. 1, a semiconductor device 7 is manufactured byconnecting a semiconductor element 1 onto a frame 2 by solder 3,wire-bonding an inner lead of a lead 5 and an electrode of thesemiconductor element 1 by a wire 4, and then sealing these componentsby sealing resin 6 or inert gas.

The semiconductor device 7 is reflow soldered using Sn—Ag—Cu seriesmedium-temperature lead-free solder to a printed circuit board. Themelting point of the Sn—Ag—Cu series lead-free solder is as high asabout 220° C., and it is supposed that a connecting portion is heated upto 260° C. at the reflow connection. Therefore, for the temperaturehierarchy, high-lead solder having a melting point of 290° C. or higheris used in the die bonding of a semiconductor element in a semiconductordevice. The high-lead solder contains lead of 85 wt.% or more as itsconstituent, and the environmental load of the high-lead solder islarger than that of Sn—Pb eutectic solder that has been prohibited bythe RoHS directive that took effect in July, 2006. Therefore, thedevelopment of a substitute connecting material to replace the high-leadsolder has been desired.

At present, the melting point of the Sn—Ag—Cu series solder that hasbeen already developed is 260° C. or lower. Therefore, if the solder isused in the die bonding of a semiconductor element, it is melted in thesecondary mounting (maximum temperature: 260° C.). In the case where asurrounding area of the connecting portion is molded with resin, whenthe inner solder is melted, due to the volume expansion in the melting,the so-called flash occurs in some cases as shown in FIG. 2, in whichthe solder 3 leaks from the interface between the sealing resin 6 andthe frame 2. Alternatively, if not leaks, the action of leakage occurs,and as a result, a large void 8 is formed in the solder after itssolidification, so that a defective product is produced. As candidatesof the substitute material, Au series solders such as Au—Sn, Au—Si andAu—Ge, Zn and Zn—Al series solders, and Bi, Bi—Cu, and Bi—Ag soldershave been reported, and further examination has been made all over theworld.

However, the Au series solder contains Au of 80 wt.% or more as itsconstituent, and thus it lacks versatility in terms of cost. The Biseries solder has a heat conductivity of about 9 W/mK which is lowerthan that of the current high-lead solder, and it is supposed that theapplication thereof to a power semiconductor device, a power module andothers requiring high heat dissipation characteristics is difficult.Further, although Zn and Zn—Al series solders have a high heatconductivity of about 100 W/mK, the solder wettability thereof is low(in particular, Zn—Al series solder) and the solder itself is hard, andthere occurs a problem that a semiconductor element is frequently brokendue to the thermal stress at the time of cooling after the connection.

In Japanese Patent Application Laid-Open Publication No. 2002-358539(Patent Document 1) and Japanese Patent Application Laid-OpenPublication No. 2004-358540 (Patent Document 2), by using an alloyconsisting of Al of 1 to 7 wt.%, Mg of 0.5 to 6 wt.%, Ga of 0.1 to 20wt.%, P of 0.001 to 0.5 wt.% and the balance of Zn, an alloy consistingof Ge of 2 to 9 wt.%, Al of 2 to 9 wt.%, P of 0.001 to 0.5 wt.% and thebalance of Zn, or an alloy consisting of Ge of 2 to 9 wt.%, Al of 2 to 9wt.%, Mg of 0.01 to 0.5 wt.%, P of 0.001 to 0.5 wt.% and the balance ofZn, the wettability of the Zn series solder alloy to Cu and Ni isimproved and the melting point thereof is decreased. However, since Aland Mg are contained, an Al oxide film and an Mg oxide film are formedon a surface of the melting portion by the heating in the connection.Since these films decrease the wetness, there is the possibility thatthe sufficient wetness cannot be obtained unless the film ismechanically broken by scrubbing or the like. Further, since noimprovement is achieved in the hardness of the solder, the improvementfor the breakage of a semiconductor element due to the thermal stress atthe time of cooling after the connection or in the temperature cyclecannot be expected.

In Japanese Patent Application Laid-Open Publication No. 2002-261104(Patent Document 3), an In, Ag or Au layer is provided for an outermostsurface of a Zn—Al series alloy, thereby suppressing the oxidation ofthe surface of the Zn—Al series alloy and improving the wettability.However, since processes such as plating and evaporation onto the Zn—Alsurface are indispensable for providing the In, Ag or Au layer, theprocesses for manufacturing the material are increased. Similarly,though the hardness can be reduced by adding In, the effect enough toprevent the breakage of the semiconductor element due to the thermalstress at the time of cooling after the connection cannot be expected.

SUMMARY OF THE INVENTION

The inventors of the present invention have thought that a Zn—Al seriesalloy can be replaced with high-lead solder. In the above-describedconventional technologies, sufficient considerations are not given tothe following points. That is, since Al is contained in a Zn—Al seriesalloy, sufficient wetness cannot be ensured. Since the surface treatmentis carried out for the Zn—Al series alloy, the processes formanufacturing the material are increased. Further, the breakage of asemiconductor element due to the thermal stress at the time of coolingafter the connection or in the temperature cycle cannot be suppressed.

In consideration of these points, an object of the present invention isto provide a connecting material capable of applying a Zn—-Al seriesalloy having a melting point of 260° C. or higher to the connection,improving the wetness at the time of connection, reducing the processesfor manufacturing the material and improving the connection reliabilityfor the thermal stress.

The above and other objects and novel characteristics of the presentinvention will be apparent from the description of this specificationand the accompanying drawings.

The typical ones of the inventions disclosed in this application will bebriefly described as follows.

The present invention provides a connecting material having a Zn seriesalloy layer formed on the outermost surface of an Al series alloy layer.In particular, the connecting material in which an Al content of the Alseries alloy layer is 99 to 100wt.% and the connecting material in whicha Zn content of the Zn series alloy layer is 90 to 100wt.% are provided.

Further, the present invention provides a manufacturing method of aconnecting material in which a connecting material having an Al seriesalloy layer formed on a Zn series alloy layer and another Zn seriesalloy layer formed thereon is manufactured by a clad rolling or apressure forming.

Further, the present invention provides a semiconductor device in whicha semiconductor element is connected to a frame by the connectingmaterial (die-bonding structure), a semiconductor device in which ametal cap is connected to a substrate by the connecting material(hermetic sealing structure) and a semiconductor device in which asemiconductor element is connected by the connection material used asbumps (flip-chip mounting structure).

These and other objects, features and advantages of the invention willbe apparent from the following more particular description of preferredembodiments of the invention, as illustrated in the accompanyingdrawings.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 is a diagram showing a structure of a conventional semiconductordevice;

FIG. 2 is a diagram for describing the flash caused by remelted solderin the semiconductor device in FIG. 1;

FIG. 3 is a diagram for describing the clad rolling in an embodiment ofthe present invention;

FIG. 4 is a diagram for describing the pressure forming in theembodiment of the present invention;

FIG. 5 is a diagram showing a cross section of the connecting materialaccording to the embodiment of the present invention;

FIG. 6 is a diagram showing the configuration of the connecting materialin FIG. 5;

FIG. 7 is a diagram showing a cross section of a semiconductor deviceusing the connecting material in FIG. 6 (examples 1 to 12) in theembodiment of the present invention;

FIG. 8 is a diagram showing a picture of a cross section of a connectingportion in the connecting material in the semiconductor device in FIG.7;

FIG. 9 is a diagram showing the evaluation results of the wettabilityand the reflow test in the semiconductor device in

FIG. 7 together with the results in the comparison examples;

FIG. 10 is a diagram showing a cross section of another semiconductordevice using the connecting material in FIG. 6 (examples 13 to 24) inthe embodiment of the present invention;

FIG. 11 is a diagram showing a metal cap integrated with a connectingmaterial in the semiconductor device in FIG. 7;

FIG. 12 is a diagram showing the evaluation results of the wettabilityin the semiconductor device in FIG. 10 together with the results in thecomparison examples; and

FIG. 13 is a diagram showing a cross section and a mounting structure ofstill another semiconductor device using the connecting material in FIG.6 in the embodiment of the present invention.

DESCRIPTIONS OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings. Note that componentshaving the same function are denoted by the same reference symbolsthroughout the drawings for describing the embodiment, and therepetitive description thereof will be omitted.

(Outline of the Embodiments of the Present Invention)

The first invention is to provide a connecting material having a Znseries alloy layer formed on the outermost surface of an Al series alloylayer. In the case of a Zn—Al alloy, since Al is contained, an Al oxidefilm is formed on the surface at the moment of melting. Therefore,unless the film is mechanically broken, the sufficient wetness cannot beobtained. On the other hand, in the present invention, the surface ofthe connecting material is the Zn series alloy containing only a littleamount of Al regarded as an impurity. Therefore, sufficient wetness canbe ensured before the Zn series alloy and the Al series alloy arereacted to from an Al oxide film in the connection. Also, since themelting portion turns to a Zn—Al series alloy in the connection, themelting point thereof decreases to about 380° C. Accordingly, since itis lower than the melting point of Zn, that is, 420° C., the thermalstress generated at the time of cooling after the connection can bereduced compared with that of pure Zn, and the breakage of asemiconductor element can be suppressed. By leaving an Al alloy layer atthe time of connection, the soft Al functions as a stress buffermaterial, and thus, the connection reliability can be improved. Even ifthe temperature is not increased to 420° C. which is the melting pointof Zn in the connection, since the diffusion proceeds between the Znlayer and the Al layer in contact with each other if the temperature is380° C. or higher, the Zn—Al eutectic crystal having the melting pointof 380° C. is formed, and hence, the connection is achieved.

The second invention is to provide a connecting material in which an Alcontent of the Al series alloy layer is 99 to 100 wt.%. The closer to100% the purity of Al becomes, the softer the material becomes, and thestress buffering function can be achieved easily. Meanwhile, when the Alpurity is less than 99 wt.%, since the 0.2% offset yield strengthbecomes an undesirable value and the hardness is increased, the stressbuffering function is difficult to obtain. The 0.2% offset yieldstrength is preferably 30 N/mm² or less. The thickness of the Al layeris preferably 30 to 200 μm. When the thickness thereof is 30 μm or less,since the thermal stress cannot be sufficiently buffered, the chip crackoccurs in some cases. When the thickness thereof is 200 μm or more,since Al, Mg, Ag and Zn have a thermal expansion rate higher than thatof a Cu frame, the effect of the thermal expansion is increased and theproblem of the decrease in reliability due to the occurrence of the chipcrack or the like may occur.

The third invention is to provide a connecting material in which a Zncontent of the Zn series alloy layer is 90 to 100 wt.% (other thanprincipal constituent, an Al content is less than 0.01 wt.%). When Al of0.01 wt.% or more is contained in the Zn series alloy, there is thepossibility that the preferable wetness cannot be obtained due to theincrease of the amount of an Al oxide film on the surface of theconnecting material at the time of connection. The thickness of the Znseries alloy layer is preferably 5 to 100 μm. When the thickness thereofis less than 5 μm, it is difficult to ensure the wetness in the entireconnecting portion.

The fourth invention is to provide a manufacturing method formanufacturing a connecting material having an Al series alloy layerformed on a Zn series alloy layer and another Zn series alloy layerformed thereon by the clad rolling. As shown in FIG. 3, when the cladrolling is performed using a roller 103, Zn series alloy layers 101 aand an Al series alloy layer 102 a are brought into contact with eachother and are largely deformed by pressure. Therefore, the oxide filmformed on the surfaces of the Zn series alloy layers 101 a and the Alseries alloy layer 102 a is broken, and the metal junction is made bythe new surfaces. In the clad rolling, the thermal load at a temperaturein which the diffusion of Zn and Al becomes significant is not applied.Therefore, Al does not diffuse in the Zn layer disposed on the surfaceand does not reach the outermost layer, and the good wetness can beobtained at the time of connection.

The fifth invention is to provide a manufacturing method formanufacturing a connecting material having an Al series alloy layerformed on a Zn series alloy layer and another Zn series alloy layerformed thereon by the pressure forming. As shown in FIG. 4, when thepressure forming is performed using a pressure forming machine 104, Znseries alloy layers 101 b and an Al series alloy layer 102 b are broughtinto contact with each other and are largely deformed by pressure.Therefore, the oxide film formed on the surfaces of the Zn series alloylayers 101 b and the Al series alloy layer 102 b is broken, and themetal junction is made by the new surfaces. In the pressure forming, ifthe thermal load is reduced to a temperature level in which thediffusion of Zn and Al is not significant, Al does not diffuse in the Znlayer disposed on the surface and does not reach the outermost layer,and the good wetness can be obtained at the time of connection.

Hereinafter, embodiments and examples based on the above-described firstto fifth inventions will be specifically described. Herein, thedescriptions will be made based on the connecting material used in thedie bonding of a semiconductor device, a power semiconductor device anda power module and manufactured by the clad rolling.

Embodiment

FIG. 5 shows a cross section of a connecting material according to theembodiment of the present invention. In the connecting materialaccording to the present embodiment, a Zn series alloy layer (simplyreferred to as Zn layer or Zn) 101 as a lower layer, an Al series alloylayer (simply referred to as Al layer or Al) 102 as an intermediatelayer and a Zn series alloy layer (simply referred to as Zn layer or Zn)101 as an upper layer are formed. As shown in FIG. 3 described above,this connecting material is manufactured by stacking the Zn series alloylayer 101 a, the Al series alloy layer 102 a and the Zn series alloylayer 101 a and then performing the rolling process, that is, the cladrolling.

FIG. 6 shows all the connecting materials (referred to as clad material)thus manufactured. In the clad material 1, the thicknesses of the Znlayer, the Al layer and the Zn layer are 10, 50 and 10 μm, respectively.In the clad material 2, the thicknesses thereof are 20, 50 and 20 μm,and in the clad material 3, the thicknesses thereof are 20, 100 and 20μm, respectively.

Examples 1 to 12

In the examples 1 to 12, as shown in FIG. 7, the connecting material 10is used for the die bonding of the semiconductor device 11. Thissemiconductor device 11 includes a semiconductor element 1, a frame 2connecting the semiconductor element 1, a lead 5 whose one end functionsas an external terminal, a wire 4 connecting the other end of the lead 5and an electrode of the semiconductor element 1, and a sealing resin 6which seals the semiconductor element 1 and the wire 4, and thesemiconductor element 1 and the frame 2 are connected by the connectingmaterial 10.

In the manufacture of the semiconductor device 11, the connectingmaterial 10 is supplied onto the frame 2 made of solid Cu or the frame 2on which the Ni, Ni/Ag or Ni/Au plating is performed and thesemiconductor element 1 is placed thereon, and thereafter, the heatingis performed at 400° C. for 1 min. in an N₂ atmosphere while applyingpressure, whereby the semiconductor element 1 is die-bonded. FIG. 8shows the cross section of the connecting portion at that time. A Zn—Alalloy layer formed by the reaction between Zn and Al at the time ofconnection is formed between the frame 2 and an Al layer of theconnecting material 10. The same is true between the semiconductorelement 1 and the Al layer of the connecting material 10. Thereafter,the semiconductor element 1 and the lead 5 are wire-bonded by the wire4, and are sealed with the sealing resin 6 at 180° C.

FIG. 9 shows the evaluation results of the wettability at the time ofthe die bonding and the connection durability after performing thereflow test with the maximum temperature of 260° C. or higher for thesemiconductor device three times, with respect to the examples 1 to 12(using clad materials 1, 2 and 3 in FIG. 6). The wettability isevaluated as 0 when 90% or more of the wetness to an area of asemiconductor element is obtained, evaluated as Δ when less than 90% to75% or more of the wetness is obtained, and evaluated as x when thewetness is less than 75%. With regard to the reflow test at 260° C.(maximum temperature), the examples where the connection area after thereflow test is decreased by 5% or more in comparison to the connectionarea before the reflow test are evaluated as x and the examples where itis decreased by less than 5% are evaluated as O.

According to the evaluation results, when the clad materials 1 to 3(Zn/Al/Zn) are used for the connection, the wetness of 90% or more canbe obtained for the frames having the Ni, Ni/Ag, or Ni/Au plating.However, for the frames made of solid Cu, the wetness is about 80% andis evaluated as Δ. With regard to the reflow test at 260° C., there isno change in the connection area in all of the examples 1 to 12.

Meanwhile, in the comparison examples 1 to 4 where the conventionalconnecting material (Zn—6Al (wt.%)) is used, a hard Al oxide film isformed on the surface of the melt Zn—Al alloy.

Therefore, the wetness is less than 75% for all the frames. Inparticular, in the cases of the solid Cu frame and the Ni plating frame,almost no wetness can be obtained. In the comparison examples 5 to 8using the conventional connecting material (Zn), 90% or more of thewetness can be obtained when the connection is performed at thetemperature of the melting point of Zn, that is, 420° C. or higher.However, the thermal stress generated due to the difference in thermalexpansion rate between the semiconductor element and the Cu frame at thetime of cooling after the connection cannot be alleviated, and thesemiconductor element is broken in some examples. When semiconductordevices are manufactured using the semiconductor elements saved from thebreakage and the reflow test is performed thereto, the breakage of thesemiconductor elements is observed.

As described above, according to the examples 1 to 12, when thesemiconductor material 10 of the present embodiment is used for the diebonding of the semiconductor device 11, since a Zn series alloy layercontaining 0.01 wt.% or less of Al is formed on the outermost surface ofan Al series alloy layer, the formation of an Al oxide film on thesurface of the connecting material at the time of connection issuppressed, and the preferable wetness that cannot be obtained with theZn—Al alloy can be obtained. Further, when an Al series alloy layer isleft after the connection, since the soft Al functions as a stressbuffer material, the high connection reliability can be achieved.

Examples 13 to 24

In the examples 13 to 24, as shown in FIG. 10, the connecting material10 a of the present invention is used as the sealing material of asemiconductor device 21 requiring the hermetic sealing. Thissemiconductor device 21 includes a semiconductor element 1, a modulesubstrate 23 connecting the semiconductor element 1, a lead 5 whose oneend functions as an external terminal, a wire 4 connecting the other endof the lead 5 and an electrode of the semiconductor element 1, and ametal cap 22 which hermetically seals the semiconductor element 1 andthe wire 4 and is connected to the module substrate 23, and the modulesubstrate 23 and the metal cap 22 are connected by the connectingmaterial 10 a. Note that, in the semiconductor device 21, chipcomponents and others are also connected onto the module substrate 23.

In the manufacture of the semiconductor device 21, after thesemiconductor element 1, the chip components and others are connected tothe module substrate 23 by an Sn series lead-free solder 3, conductiveadhesive, a Cu powder/Sn powder compound material or the like, theconnecting material 10 a is placed between the module substrate 23 andthe metal cap 22, and the module substrate 23 and the metal cap 22 areconnected while applying pressure at 400° C.

Note that, with regard to the metal cap, a metal cap 22 a integratedwith a connecting material composed of a metal alloy 24 such as kovar orinvar, an Al series alloy layer 102 and a Zn series alloy layer 101processed together by the clad rolling as shown in FIG. 11 can be usedfor achieving the hermetic sealing.

FIG. 12 shows the evaluation results of the wettability at the time ofdie bonding with respect to the examples 13 to 24 (using the cladmaterials 1, 2 and 3 in FIG. 6). The wettability is evaluated as O whenthe wetness capable of maintaining the hermeticity to the sealing areacan be obtained, and evaluated as x when the hermeticity cannot bemaintained due to a void, crack and others.

According to the evaluation results, when connecting materials such asthe clad materials 1, 2 and 3 (Zn/Al/Zn) are used for the connection,the wetness capable of sufficiently maintaining the hermeticity can beobtained for the frames having the Ni, Ni/Ag or Ni/Au plating. However,for the solid Cu frame, the evaluation is x due to the insufficientwetness and the formation of voids.

Meanwhile, in the comparison examples 9 to 12 where the conventionalconnecting material (Zn—6Al (wt.%)) is used, a hard Al oxide film isformed on the surface of the melt Zn—Al alloy. Therefore, thehermeticity cannot be maintained due to the insufficient wetness and theformation of voids.

As described above, according to the examples 13 to 24, when theconnecting material 10 a of the present embodiment is used as thesealing material of the semiconductor device 21, the formation of an Aloxide film on the surface of the connecting material at the time of theconnection can be suppressed, and the wetness capable of sufficientlymaintaining the hermeticity can be obtained.

In the semiconductor device 21 shown in FIG. 10, the connecting material10 of the present invention can be used instead of the lead-free solder3 for the connection between the semiconductor element 1 and the modulesubstrate 23. In this case, the effects similar to those of theabove-described examples 1 to 12 can be achieved.

Other Example

In other example, the connecting material 10 b of the present inventionis used as a bump in the semiconductor device 31 requiring the flip-chipmounting as shown in FIG. 13. The semiconductor device 31 includes asemiconductor element 1, and the semiconductor element 1 and a substrate34 on which the semiconductor element 1 is to be mounted are connectedby the connecting material 10 b.

In the manufacture of the semiconductor device 31, the connectingmaterial 10 b is placed between a pad obtained by performing an Ni orNi/Au plating 36 onto a Cu wiring 35 of the substrate 34 and anelectrode obtained by performing a Zn plating 33 onto an Al wiring 32 ofthe semiconductor element 1, and the substrate 34 and the semiconductorelement 1 are connected while applying pressure at 380° C.

Also in this example, when the connecting material 10 b of the presentembodiment is used as the bump of the semiconductor device 31, theformation of an Al oxide film on the surface of the connecting materialat the time of the connection can be suppressed, and the preferablewetness can be obtained.

In the foregoing, the invention made by the inventors of the presentinvention has been concretely described based on the embodiments.However, it is needless to say that the present invention is not limitedto the foregoing embodiments and various modifications and alterationscan be made within the scope of the present invention.

More specifically, in the description above, although the application ofthe present invention has been described with using the die boding of asemiconductor device as an example, the present invention can be appliedto various types of semiconductor devices as long as the semiconductordevice is die-bonded. Such semiconductor devices include, for example,an alternator diode, an IGBT module, a front-end module such as an RFmodule, a power module for a vehicle, and others.

Further, in the foregoing description, the case where a semiconductordevice is reflow-mounted onto a module substrate has been described.However, the present invention can be applied to the case where thesemiconductor device is used for the MCM (Multi Chip Module) structure.

As described above, the connecting material of the present invention canbe effectively used for the die bonding, the sealing material for thehermetic sealing, and the flip-chip bonding of a semiconductor device, apower semiconductor device, a power module and others.

The effects obtained by typical aspects of the present invention will bebriefly described below.

According to the present invention, since the connecting material havinga Zn series alloy layer formed on the outermost surface of an Al seriesalloy layer is used, the formation of an Al oxide film on the surface ofthe connecting material at the time of connection can be suppressed, andthe preferable wetness can be obtained. Also, since the Al series alloylayer functions as a stress buffer material after the connection, thehigh connection reliability can be achieved. As a result, it becomespossible to apply a Zn—Al series alloy having a melting point of 260° C.or higher to the connection, improve the wetness at the time ofconnection, reduce the processes for manufacturing the material andimprove the connection reliability for the thermal stress.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description and all changeswhich come within the meaning and range of equivalency of the claims aretherefore intended to be embraced therein.

What is claimed is:
 1. A connecting material, comprising: an Al seriesalloy layer; and a Zn series alloy layer formed on an outermost surfaceof the Al series alloy layer.
 2. The connecting material according toclaim 1, wherein an Al content of the Al series alloy layer is 99 to 100wt.%.
 3. The connecting material according to claim 1, wherein a Zncontent of the Zn series alloy layer is 90 to 100 wt.%.
 4. A method formanufacturing a connecting material, wherein the connecting material isformed by stacking an Al series alloy layer on a first Zn series alloylayer, stacking a second Zn series alloy layer on the Al series alloylayer, and then performing a clad rolling or pressure forming.
 5. Asemiconductor device, comprising: a semiconductor element; a frameconnecting the semiconductor element; a lead whose one end functions asan external terminal; a wire connecting the other end of the lead and anelectrode of the semiconductor element; and a resin sealing thesemiconductor element and the wire, wherein a connecting materialconnecting the semiconductor element and the frame includes an Al seriesalloy layer and a Zn series alloy layer formed on an outermost surfaceof the Al series alloy layer.
 6. A semiconductor device, comprising: asemiconductor element; a substrate connecting the semiconductor element;a lead whose one end functions as an external terminal; a wireconnecting the other end of the lead and an electrode of thesemiconductor element; and a metal cap hermetically sealing thesemiconductor element and the wire and connected to the substrate,wherein a connecting material connecting the substrate and the metal capincludes an Al series alloy layer and a Zn series alloy layer formed onan outermost surface of the Al series alloy layer.
 7. The semiconductordevice according to claim 6, wherein the connecting material connectingthe semiconductor element and the substrate includes an Al series alloylayer and a Zn series alloy layer formed on an outermost surface of theAl series alloy layer.
 8. A semiconductor device, comprising: asemiconductor element, wherein a connecting material connecting thesemiconductor element and a substrate having the semiconductor elementmounted thereon includes an Al series alloy layer and a Zn series alloylayer formed on an outermost surface of the Al series alloy layer.